The present invention is a plastic form body with graphically designed surfaces and integrated electro-luminescence elements (EL elements). For example, graphic and electro-luminescence structures are placed on transparent and cold-stretchable thermo-plastic plastic foil by means of silk screen printing (serigraphy), then subjected to a pushing isostatic high-pressure deformation, stamped and placed in an injection mold and back-injected generally on the inner wall by means of suitable thermoplastic plastic resulting in a three-dimensional plastic form component with integrated EL luminous fields.
The DE 44 30 907 A1 makes a three-dimensional electro-luminescence indicator based on an electro-luminescence lights integrated in a three-dimensional formed body. The preformed electro-luminescence lights are formed in a whole piece on a substrate. The disadvantage with this is the separate design of the aforementioned light transmitting layer and the electro-luminescence light and their exact positioning to each other that results in an expensive and costly production process.
A similar three-dimensional electro-luminescence indicator is made known with WO-A-94/14180. Here also, prefabricated, foil formed electro-luminescence lights are applied on carrier material and can be formed together. This has the disadvantage that a separate design of the light transmitting layer of the carrier material and the electro-luminescence light and an exact positioning of the EL-lights in the carrier material is necessary, which makes the production expensive and cost-intensive.
Usually the decorative foils are formed after the vacuum process or the compressed air process to a three-dimensional deep-drawing formed body. Then the graphically designed thermoplastic foils are heated to a temperature above the material""s heat distortion temperature so that they can be shaped with relatively little pressure (such as vacuum). These vacuum- and compressed air processes can be used very efficiently with graphically non-critical or neutrally designed foils and form bodies, and function with vacuum processes at a medium pressure of less than 0.95 bar and with compressed air processes at an operating medium pressure of less than 6 bar.
Form components that require exact positioning of graphically designed elements and a very precise image with patterns and/or a great contour sharpness, and which must have a precise form after the deep-drawing process, the procedures of the isostatic high pressure forming according to DE 38 40 542 C1 (also in a somewhat limited way, the so-called hydro-forming) offer advantages.
The production of these types of electro-luminescence fields in connection with the graphic design, must take the very precise positioning of the individual presses and processes together into consideration. The positioning of the nearly transparent ITO-paste graphics, especially, presents a fundamental criterion of quality. U.S. Pat. No. 5,583,394 makes a procedure of recording known that provides invisible positioning markers in a visible light, which, by means of a corresponding light source, are identified with an ultra-violet light for respective reading sensors and, thus, make an exact positioning possible. The disadvantage is that these registration marks can only be applied with additional operating steps and used only with special light sources and special positioning sensors.
Electro-luminescence screen printing pastes are generally made up of inorganic substances and, here again, are very pure ZnS, CdS, ZnxCd1xe2x88x92xS, etc. Compounds of the II and VI group of the periodic system are of importance that generally are doped or activated with Cu, Mn, Ag, etc. Normal colors are yellow, green, green-blue, blue-green and white.
Respective to the state of technology, these types of luminescence pigments can be microencapsulated with diameters of typically 15 to 60 xcexcm in order to be added to various silk screen printing inks (colors), or non-encapsulated, certainly taking the special hygroscopic characteristics of the ZnS pigments into consideration. Fixing agents are used that, on the one hand, provide good adhesion for the so-called ITO-layers, continue to insulate well, reinforce the dielectric, in order to improve the puncture or disruptive strength with high electrical field strengths and, additionally, have a good water vapor block and so additionally protect the phosphorous pigments to lengthen their life expectancy.
Generally, phosphorous pastes of these types are put on by screen printing or other coating procedures, such as brushing, rolling, coil coating, etc. on transparent plastic foils or glass, which again have a wide transparent electric conducting layer and with it the electrodes for the visual side. Finally, the dielectric and the back-side electrode are produced by printing (press) techniques and/or laminating techniques.
The usual ITO-paste layers (or also tin oxide coatings, etc.) applied by screen printing, however, have the advantage of extensive random geometrical design possibilities, but the vapor-deposited or sputter-deposited transparent and electrical-conducting layers still have the disadvantage of having less optical transparency or translucency and, furthermore, have a much lesser degree of conducting capacity, of at the most some 100 Ohm per square in comparison to some less than 10 Ohm per square with ITO-polyester foil or some less Ohm per square with ITO-coated glass. But the glass can have pastes added (for example, In2O3/SnO2), which must, however, be fired at over 500xc2x0 C. and, therefore, can already deliver with a 0.25 xcexcm film strength, an optical transparency of greater than 95% and a conducting capacity of a single layer is from 500 to 1000 Ohm per square.
The purpose of the present invention is to produce a three-dimensional graphically designed plastic form body with integrated electro-luminescence elements economically, with a longer life expectancy, increased luminous intensity and guaranteed performance regardless of the existing electric power supply.
In the framework of the present invention it has been determined that the new types of electro-luminescence screen printing inks (colors), new types of ITO (Indium-Tin-Oxide) colors, and new types of insulation and dielectric colors, together with the printing format can be applied, and then the high-pressure formation and the back-injection can be completed by means of thermoplastic plastics by following several ground rules without impairment to the function of the electro-luminescence elements.
According to the invention, the previously discussed procedure of the isostatic high-pressure formation is sufficient for forming the plastic components. So-called cold-stretchable plastic foils are provided with printing ink (colors) that, together with an operating temperature below the distortion temperature of the thermoplastic foil""s plastic, completes a push-type forming operation to a three-dimensional plastic form component with greater image precision.
Advantageously, isostatic high-pressure forming, especially the push-type stamping of the plastic components with preferably several 100 bar compress air (typically 50 to 300 bar), very short cycle times with outstanding controlled and even formation, which results in greater image accuracy and, furthermore, produces the same types of formed components with less heat (which means the time-consuming cool-down phase is discontinued), outstanding dimensionally stable formed bodies and constant contours (which remain the same), which is really essential for the final stamping process and the insertion into the injection molding die, increasing the quality.
Other processes for forming the plastic foil three-dimensionally are also possible (for example, mechanical shaping or mechanical stamping methods). A re-forming of the plastic foil placed in an injection molding die can itself result from the injection of the thermoplastic plastic material.
The present invention is also based on the cognition that for a product of this type, known screen printing pastes with phosphorous pigments, especially in the microencapsulated form (but also in the non-encapsulated form) based on respective doped compounds of the II and VI groups of the periodic system, especially in forms with Cu, Mn, Ag, etc., doped ZnS pigments in combination with special cold-formable polycarbonate substrate or the various mixtures of polycarbonate and polyethyleneterephthalate (PETP) or polyalkyleneterephthalates are very suitable. Mixtures of additional luminous colors, especially those that, through the electro-luminescence radiation for light excitation and release of respective radiation with wide ranges of discretionary spectrals (as narrow banded wave-length peaks) work very positively and effectively.
In another development of this procedure, the color printing can be imbedded sandwich-like between two layers of foil material. This results in less problems with the back-injection of thermoplastic plastics, which in this case of color printing, are better protected by the additional foil against distortion and melting in the injection area.
In another typical embodiment, a layout of a luminous field has not only two electrical connections, but many fields; for example, with various color luminous fields, such as lettering and/or symbols.
In relation to the necessary position exactness, the individual printings have been established within the framework of the present invention; that the registration of the various layers and processes can be realized manually in general by means of registering marks in visible luminous areas (and also automatically), and that each layer based on the nearly transparent ITO-paste can be controlled and registered very well concerning the preciseness of the position and the constancy of the process by means of electrical test configurations in connection with conducting paste structures. Additionally, the allowable surface resistance and/or contact or transition resistance of the ITO-paste contacts to the conductor will be evaluated and recorded.